Descriptions in antiquity of the execution cross
Descriptions in antiquity of the execution cross, whether by Christians or non-Christians, present the instrument ordinarily used in putting people to death by crucifixion as composed of two wooden pieces. Whether the two pieces of timber of the normal execution cross were permanently conjoined or were merely put together for the purpose of the execution is not stated.
Source: Wikipedia — Descriptions in antiquity of the execution cross (CC BY-SA 4.0)